(1) Field of the Invention:
This invention relates to a webbing retractor suitable for use in a seat belt system for protecting an occupant in the event of a vehicular emergency, and specifically to a take-up spindle for such a webbing retractor, which is constructed of a shaft and a sleeve and can effectively prevent a webbing from being pulled out of the retractor even after the take-up spindle has been stopped from rotating in a webbing-releasing direction, in other words, can achieve effective prevention of so-called tightening and release of the webbing wound on the take-up spindle.
(2) Description of the Related Art:
Webbing retractors which have heretofore been known to be useful in a seat belt system for protecting an occupant in the event of a vehicular emergency include those of a type such that a take-up spindle is rotatably supported on a frame to be mounted on a vehicle body, an occupant-restraining webbing is wound up from one end thereof on the take-up spindle, and a mechanism is mounted on an end portion of the take-up spindle so as to prevent the take-up spindle from rotating in a webbing-releasing direction.
The securement structure between a webbing and a take-up spindle in a webbing retractor of the above type will be described in detail. One type of securement structure is shown in FIG. 5 by way of example. A slot 10A in which a turned-over loop portion 14A of an end part of a webbing 14 is received and another slot 10B through which the webbing 14 extends out are formed at antipodal points of a take-up spindle 10. A holding pin 15 extends through the loop portion 14A of the webbing 14. The webbing 14 which has extended out through the slot B is wound on an outer peripheral wall of the take-up spindle 10 and is then guided out into an interior of a vehicle. Another type of securement structure is illustrated in FIG. 6 by way of example. A take-up spindle 10 is constructed of a sleeve 13 and a shaft 11 inserted in a central hole of the sleeve 13. Slots 11A,11B are formed through the shaft 11 at points not antipodal to each other, while slots 13A,13B are formed through the sleeve 13 at points not antipodal to each other. The slots 11A and 13A are angularly in registration, while the slots 11B and 13B are are angularly in coincidence. A turned-over loop portion 14A of an end part of a webbing 14 is received in the slots 13A,11A on one side of the take-up spindle 10. The webbing 14 extends out through the slots 13B,11B on another side of the take-up spindle.
Irrespective of their types, the above-described conventional webbing retractors contains a spacing C in the slots 10A, 11A and 13A of the take-up spindle 10. These slots 10A, 11A and 13A are located on the side that the holding pin 15 is secured. Described more specifically, the spacing C is defined by the turnedover loop portion 14A of the end part of the webbing 14 and the inner side walls or edges of the slots 10A, 11A and 13A.
When a large tensile force is applied to the webbing 14 in a state that the take-up spindle 10 has been locked from rotating in the webbing-releasing direction in the event of an emergency, a webbingtightening force is applied to the take-up spindle 10 so that the take-up spindle 10 may hence be deformed to reduce the spacing C.
When the take-up spindle 10 undergoes such a deformation, its core diameter is reduced to allow the webbing 14 to extend out, whereby the so-called tightening and release phenomenon takes place and locking effects of an associated webbing retractor could be impaired.